The present invention relates to a method of cushioning commodities to be packaged or crated by cellular plastic material which is foamed in place around the commodities in cartons, boxes or other types of containers.
An advantage of foamed-in-place cushions in the packaging field is that a commodity which is surrounded by such cushioning or padding means (which, in turn, is confined in a container) is adequately shielded against shocks at all sides which are surrounded by foamed plastic material. This is due to the fact that foaming in place causes the cellular plastic material to fill the space or spaces between the external surface of the commodity and the internal surface of the container.
In accordance with a presently known packaging technique which resorts to foamed-in-place cushioning materials, a flexible hose or an analogous envelope for the constituents of cellular plastic material is inserted into a container prior to insertion of the commodity to be packaged. The envelope is sealed and the confined material is caused or allowed to foam. When the foamed material reaches the desired stability (but prior to completion of the foaming step), the commodity to be packaged is placed onto such foamed material and a second envelope (again containing the constituents of cellular plastic material) is placed on top of the commodity. The second envelope is thereupon closed and the container is also closed. The foaming of material in both envelopes is completed while the container is closed whereby such material forms a composite cushion which fills or substantially fills the space between the commodity and the container.
The just described conventional procedure exhibits several serious drawbacks. Thus, a certain interval of time must elapse between the insertion of the first envelope and the insertion of a commodity to be packaged because the foamed material in the first envelope must acquire a certain stability which suffices to insure that such material will maintain the inserted commodity at an optimum distance from the bottom wall of the container. Moreover, the insertion of a commodity on top of the material in the first envelope must be timed with utmost care because premature insertion results in excessive flattening of the material in the first envelope whereas delayed insertion enables the cushion below the inserted commodity to assume a condition in which it maintains the commodity too close to the cover, i.e., the second cushion in the envelope on top of the commodity is not permitted to acquire an optimum thickness. Still further, the just described procedure often results in lateral shifting of inserted commodities. In order to insure satisfactory cushioning of commodities (e.g., sensitive pumps, valves or the like and/or their parts), the operation must be controlled by highly skilled and reliable attendants.
It is also known to utilize prefabricated cushions which are placed onto the bottom wall of the container prior to insertion of the commodity. The next-following part of the packaging operation is carried out in the same way as described above, i.e., an envelope containing the constituents of cellular plastic material is placed on top of the commodity, the container is closed and the foaming in place proceeds in order to obtain a second cushion which fills the space around the commodity at a level above the prefabricated bottom cushion. The just described procedure exhibits the advantage that the commodity is more likely to be located in the optimum position. However, the cost of packaging is much higher because of the need for prefabricated cushions as well as for facilities in which the prefabricated cushions are stored. Also, the cushioning or padding effect of a prefabricated cushion is often quite different from the effect of a cushion which is foamed in place so that the commodity which is confined between a prefabricated cushion and a foamed-in-place cushion is likely to change its position and/or orientation during transport and/or other manipulation of the container. Therefore, it is customary to employ auxiliary equipment which insures (or is intended to insure) retention of the commodity in an optimum position. The provision of auxiliary equipment contributes to the cost of the packaging operation. Still further, the hardness of a prefabricated cushion must be selected in dependency on the weight of the commodity to be supported thereby because such prefabricated cushion supports the entire commodity in the course of the packaging operation. This means that, if the weight of commodities to be packaged is not uniform, it is necessary to furnish an assortment of prefabricated cushions each of which exhibits a different resistance to deformation under weight.